/**
 * @param {string} s
 * @param {string} t
 * @return {character}
 */
var findTheDifference = function(s, t) {
    if(s.length===0){
        return t;
    }
    let ss=Array.from(s).sort().join("")
    let st=Array.from(t).sort().join("")
    let s_length=ss.length;
    for(let index=0;index<=s_length;index++){
        if(ss[index]!==st[index]){
            return st[index];
        }
    }
};

findTheDifference('opwquirety','poiuytrewqf')
